It is proposed to apply the concept of active-site-directed irreversible inhibitors as a means for the preparation of anti-progestational compounds which will be useful as contraceptive agents. Long chain esters of 17-alpha-ethynyl-19-nortestosterone which terminate in an electrophile will be prepared. It is postulated that these compounds will bind to the cytoplasmic progesterone receptor and that the electrophile will undergo reaction with a nucleophilic group outside of the binding site resulting in irreversible attachment of the molecule to the receptor protein. If this attachment takes place in such a manner as to prevent the complex from being translocated to the nuclear acceptor sites an overall anti-progestational activity will be observed. The compounds which are prepared will be tested for their ability to compete either reversibly or irreversibly with tritiated progesterone for the progesterone receptor. Selected compounds will be tested for their ability to enter the nucleus and bind to the chromatin. The candidate compounds will be tested for the progestational and anti-progestational activity. Compounds of interest will be tested for anti-fertility activity. It is anticipated that compounds which irreversibly bind to the progesterone receptor will be useful tools in elucidating the mechanism of steroid hormone-receptor action.